Eating raw fish, also known as sashimi or sushi, is becoming increasingly popular. Raw fish can be very tasty and nutritious. However, there are also some potential health risks with eating raw fish, especially related to parasites and bacteria. This article explores whether it is safe to eat previously frozen fish raw.
Is it safe to eat frozen fish raw?
Many people wonder if it is safe to eat fish raw that was previously frozen. The good news is that freezing fish can actually kill any parasites or bacteria that may be present, making it safer for consumption. Here are some key points on the safety of eating previously frozen fish raw:
- Freezing fish at -4°F (-20°C) or below for 7 days (total time), or freezing at -31°F (-35°C) or below until solid and storing at -31°F (-35°C) or below for 15 hours, is sufficient to kill parasites. This is according to FDA guidelines.
- Freezing can also kill most bacteria present in fish. Certain bacteria can sometimes survive freezing, but proper handling thaws and preparation of the fish reduces risk.
- Fish that has been previously frozen by a reputable retailer, according to proper freezing guidelines, is generally considered safe to eat raw under FDA standards.
- It is still important to ensure the fish is high-quality, properly thawed, and prepared hygienically to reduce risk of illness.
So in summary, yes fish that has been properly frozen can generally be eaten raw, as the freezing process destroys parasites and bacteria that could make you sick. But it is still important to take care in thawing, handling and preparing the fish to maximize safety.
Parasites in fish and freezing
One of the biggest concerns with eating fish raw is the risk of parasitic infection. Parasites like nematodes, cestodes, trematodes, and copepods can sometimes be present in fish, especially wild caught fish. Eating undercooked or raw fish containing live parasites can lead to parasitic infections in humans. Symptoms like abdominal pain, nausea, vomiting, diarrhea and others may occur if infected.
However, most parasites cannot survive being frozen at the appropriate temperature and duration. The FDA Food Code indicates freezing fish at -4°F (-20°C) or below for 168 hours (7 days) is sufficient to kill parasites. Alternatively, freezing at -31°F (-35°C) or below until the fish is solid and storing at -31°F (-35°C) or below for 15 hours kills parasites as well.
Most fish served raw in restaurants or sold frozen for raw consumption at retailers and markets in the U.S. has been frozen solid to meet these FDA guidelines. So frozen fish that is properly thawed and prepared following FDA guidance is considered safe for raw consumption in terms of parasites.
Common fish parasites killed by freezing
Here are some of the most common fish parasites that freezing can destroy:
- Anisakis – A nematode that can cause anisakiasis when ingested. It cannot survive freezing.
- Diphyllobothrium – A cestode that can cause diphyllobothriasis (fish tapeworm). Freezing kills this parasite.
- Cryptocaryon – A ciliate parasite that causes marine white spot disease in fish. It is killed by freezing.
- Salmon fluke – A trematode parasite that can infect humans if fish is undercooked. Freezing kills salmon fluke.
- Cod worm – A nematode parasite that can cause lumpfish disease. Freezing eradicates cod worm.
Bacteria in fish and freezing
Freezing can also significantly reduce numbers of bacteria present in fish that could potentially cause foodborne illnesses. This includes bacteria like Vibrio, Listeria monocytogenes, Clostridium botulinum, Salmonella, Shigella, Staphylococcus aureus, and Bacillus cereus.
While freezing kills most bacteria, some bacteria can occasionally survive freezing temperatures, especially if only briefly frozen. Bacteria also may recontaminate fish during the thawing process if not handled properly.
However, fish that has been frozen solid as per FDA guidelines and is properly thawed and prepared minimizes the risk of bacterial foodborne infection. Proper handling is still important though to reduce the chances of any surviving bacteria multiplying to dangerous levels before eating the thawed fish.
Key tips to minimize bacteria risk
Here are some tips to keep bacteria risk low when consuming previously frozen raw fish:
- Thaw fish properly in the refrigerator, not at room temperature where bacteria can grow rapidly.
- Avoid cross-contamination by keeping raw fish separate from ready-to-eat foods.
- Wash hands, utensils, surfaces properly after handling raw fish.
- Use thawed fish within 1-2 days and don’t refreeze.
- If making sushi, marinate/acidify fish first to further reduce bacteria.
- Cut fish properly to avoid bacterial growth in meat crevices.
- Refrigerate fish immediately until use and discard fish if smells or looks off.
Should commercially frozen fish be avoided?
Some sources advise avoiding fish labeled “commercially frozen” and only eating fish that has been frozen by consumers or at the selling retailer. However, most experts consider commercially frozen fish safe for raw consumption as long as proper FDA freezing guidelines were adhered to.
During commercial freezing, fish is frozen rapidly at very low temperatures under pressure. This quick-freezing process can kill parasites and bacteria as effectively as freezing done elsewhere, if not more so.
The concern with commercially frozen fish is more related to proper freezing temperature and duration to eradicate threats. As long as commercial processors adhere to FDA time/temperature guidelines, the frozen fish should be safe from parasites and mostly safe from bacteria as well.
Is frozen tuna safe for sushi and sashimi?
Tuna is one of the most popular fish used for sushi and sashimi. Provided the tuna has been properly frozen to eliminate parasites, previously frozen tuna is considered safe to eat raw. For example, tuna eligible for use in sushi/sashimi should have been frozen solid at -31°F (-35°C) or below for 15 hours minimum according to FDA rules.
If you buy commercially frozen tuna steaks or loins from a market or online, check that it has been flash-frozen to at least this temperature and duration. Tuna frozen for sushi is sometimes labeled as “sushi-grade” or “sashimi-grade”. This is not an official designation, but indicates the supplier has likely followed proper freezing protocols.
It is also important to thaw, prepare, and handle the tuna hygienically to prevent bacterial risks. But overall, previously frozen tuna can definitely be enjoyed raw in sushi and sashimi provided sound freezing and food safety practices are followed.
Raw fish precautions for pregnant women
It is usually recommended that pregnant women avoid consuming raw fish and shellfish due to certain foodborne illness risks. Some key precautions include:
- Avoid raw fish unless it has been frozen first as per FDA guidelines to destroy parasites.
- Avoid raw shellfish like oysters, clams and mussels.
- Cook fish to 145°F (63°C) minimum internal temperature.
- Avoid refrigerated smoked seafood unless it is in a cooked dish.
- Avoid fish with higher mercury levels, like swordfish, shark, tilefish and king mackerel.
Pregnant women usually have weakened immune systems, putting them at higher risk of foodborne illnesses. Properly frozen fish is considered safer, but cooked fish is the most recommended. Discuss your diet with your doctor for personalized pregnancy advice.
Should you freeze fish before eating raw?
Freezing fish before eating raw is an added safety precaution to kill any parasites present. However, freezing is not mandatory if you know the fish has already been properly frozen.
Most fish sold commercially for raw consumption has already been frozen solid to FDA standards. Sushi/sashimi-grade fish at markets, specialty seafood distributors and quality restaurants generally meet guidelines for parasites. Repeat freezing may not be needed if sourcing high-quality frozen fish.
That said, buying fresh fish and freezing it yourself is an option if you want extra assurance. Freeze at -4°F (-20°C) for 7 days minimum, or -31°F (-35°C) until solid and store at that temperature for 15 hours. Thaw in refrigerator before use.
While freeze-before-use is not obligatory with pre-frozen fish, it adds an extra layer of protection if you are ever unsure of the freezing history. But commercial frozen fish is generally safe without repeating the process.
Does freezing affect fish quality?
Freezing can impact the texture and flavor of fish to some degree. Freeze/thaw cycles can degrade cell structure, causing the flesh to become slightly dry and mushy. The effects depend on factors like freezing rate, storage temperature and duration.
However, modern commercial freezing methods like blast freezing and cryogenic freezing minimize quality loss. Fast freezing preserves cell structure much better. Flavor and texture changes are often subtle, and overall nutritional value is preserved.
While not identical to ultra-fresh, frozen fish still provides an enjoyable eating experience, especially with high-quality freezing processes. Any texture or flavor changes are usually a small tradeoff for the food safety benefits of proper freezing.
Tips to minimize freezing impact on fish
Some tips to reduce freezing damage when preparing fish for raw consumption:
- Freeze fish as soon as possible post-catch for freshness.
- Freeze fish quickly at very cold temperatures (e.g. -31°F).
- Avoid freeze-thaw cycles by freezing serving portions.
- Glaze frozen fish with ice to prevent freezer burn.
- Store frozen fish below 0°F at all times.
- Thaw fish gradually in the refrigerator.
- Use thawed fish promptly; avoid refreezing.
Can you eat salmon raw from the supermarket?
It is generally safe to consume raw salmon purchased from a trusted supermarket or fish market. Salmon sold commercially for consumption as sushi or sashimi should be frozen properly to eliminate parasites beforehand.
Provided the salmon is high-quality and has been frozen for the requisite time and temperature per FDA guidelines, it can be eaten raw. Be sure to inspect the fish closely and note any labeling indicating it has been previously frozen for raw consumption.
Supermarkets take care in sourcing frozen fish that is safe for such applications. But it is still smart to take precautions like thawing in the refrigerator, keeping raw salmon cool until use, separate from other foods, and cleaning surfaces/utensils after.
Tips for eating raw supermarket salmon safely
- Check for reputable seller and “sushi-grade” or “sashimi-grade” labels.
- Look for frozen solid with no signs of thawing/refreezing.
- Thaw according to guidelines in refrigerator before use.
- Keep raw fish chilled, separate from other food items.
- Discard if smells or looks off before serving.
- Clean hands, surfaces, tools thoroughly after handling.
Can you eat smoked salmon raw?
Smoked salmon that has been commercially frozen and properly processed can be eaten raw. Smoking helps prolong shelf life and enhance flavor, but does not actually cook the salmon or kill bacteria/parasites. So previously frozen salmon should still be used.
Deli-style smoked salmon that is vacuum-packed and sold refrigerated has not been frozen or heated, so it should not be eaten raw. Only smoked salmon labeled as previously frozen that has been handled and thawed safely should be consumed raw.
Smoked salmon should also smell fresh with no off odors, look firm and glossy, and feel moist. Discard if any signs of spoilage. Use safe handling as with any other raw fish.
Is it safe to eat raw fish at a restaurant?
Eating raw fish dishes like sushi and ceviche at restaurants is generally safe. Reputable restaurants take care in sourcing fish for raw consumption and have food safety protocols in place.
Restaurants should purchase high-quality frozen fish that has been handled to destroy parasites and minimize bacteria. They should thaw, prepare and serve the fish promptly under sanitary conditions. Any leftover fish should be discarded.
You can take some basic precautions as a customer as well:
- Check restaurant ratings and dining reviews beforehand.
- Ask where they source fish and their food safety methods.
- Ensure raw fish smells fresh and looks appetizing.
- Send back anything that seems questionable.
- Avoid ordering raw fish when pregnant or immunocompromised.
There is always some low risk with raw fish. But reputable restaurants follow guidelines to serve raw seafood safely along with other ready-to-eat foods.
Can thawed fish be refrozen and eaten raw?
It is not recommended to refreeze previously frozen fish that has already been thawed and then eat it raw. Refreezing thawed fish can allow bacteria like Listeria or Salmonella to multiply to unsafe levels.
The FDA Food Code states that once fish has been thawed from a frozen state, it should be consumed within 1-2 days. Refreezing after thawing could make it unsafe, especially for eating raw.
That said, fish that is still mostly frozen with ice crystals and refrigerated below 40°F could potentially be safely refrozen. But thawing and refreezing significantly increases bacterial risk, so thawed fish is best fully cooked rather than eaten raw.
Can you eat raw frozen fish?
Eating fish raw that is still in a frozen state is generally not recommended or safe. Harmful bacteria like Clostridium botulinum, the culprit behind botulism food poisoning, can actually thrive at freezing temperatures.
Freezing prevents bacteria from multiplying, but does not reliably kill all bacteria. Consuming fish raw directly from frozen allows bacteria present to avoid being destroyed by cooking. Defrosting first is safer.
There is also a physical danger of consuming frozen fish directly. The frozen tissue could cause injury to teeth, gums, mouth, esophagus and other tissues during mastication and swallowing.
For optimal safety and enjoyment, fish intended for raw consumption should be properly thawed in the refrigerator based on package directions, then promptly prepared and eaten.
Summary
In summary, previously frozen fish can be a safe and healthy choice for eating raw provided proper guidelines are followed. Commercial freezing processes destroy parasites and reduce bacterial risks to safe levels in fish. Look for reputable sourcing and quality freezing procedures. It is also important to thaw, handle, prepare and serve the fish hygienically before eating to minimize any remaining bacteria. Employing sound freezing, storage, and food safety practices makes eating raw fish that was frozen quite safe and enjoyable.
